The prior art is replete with disclosures of tamper-evident closures, formed of a cap, a tamper-evident ring and a plurality of circumferentially spaced-apart breakaway bridges or tabs interconnecting the cap and ring. One of the problems encountered in the design of such tamper-evident closures is the premature breakage of the tabs or bridge members during a capping operation, in which the closure is being applied to a container.
One solution to the problem of premature breakage of the tabs is suggested in U.S. Pat. No. 3,455,478, issued to Fields et al. In the design disclosed in that patent the breakaway tabs or bridge members are inclined in a direction which subjects them to compressive forces when the closure is rotated in a clockwise direction during capping, and which subjects them to tensile forces, which breaks them, when the cap is unscrewed in a counterclockwise direction.
Although the concept disclosed in the Fields et al. '478 patent is very desirable, there is no arrangement provided for actually limiting the amount of compressive force imposed upon the bridge members during the capping operation. This can result in the premature fracture of the bridges and/or the undesired distortion of the tamper-evident ring as it is snapped over a retaining bead on a container during a capping operation.
U.S. Pat. No. 4,505,401, issued to Berglund, also discloses a tamper-evident closure of the type employing inclined bridges between a threaded cap section and an underlying tamper-evident ring. In the embodiment shown in FIG. 3 of the Berglund '401 patent cooperating engagement means, generally referred to by the numeral 11, are provided to insure that the tamper-evident ring is entrained rotationally with the cap when the cap is being screwed onto a container. These engagement means include one or more teeth 12 on the edge of the cap skirt engaging with one or more corresponding notches 13 on the tamper-evident ring. Although this arrangement limits the amount of force imposed upon the breakaway tabs 7 during the capping operation, it is a somewhat complex arrangement, requiring the formation of interlocking members which are separate and apart from the inclined breakaway tabs.
U.S. Pat. No. 4,828,127, issued to Young et al, discloses another arrangement for securing a tamper-evident ring to a threaded cap member by inclined breakaway tabs. In this arrangement, as can be seen best in FIG. 5, the substantially vertical edge 9, provided as part of each recess 8, cooperates with a confronting vertical surface of a tooth 11 to prevent the imposition of excessive forces upon the webs 12 during a capping operation. In particular, the confronting surfaces engage each other to thereby cause the cap and retaining ring to move as a single unit during the capping operation, prior to imposing, on the interconnecting webs 12, an excessive force which will prematurely (and undesirably) fracture the webs during the capping operation. Like the arrangement disclosed in the Berglund '401 patent, structural members independent of the breakaway tabs 12 are relied upon to transmit rotational forces from the cap to the tamper-evident ring during a capping operation.